To address persistent cost and quality challenges, US policymakers have pursued multiple delivery and payment reforms. Alternative payment models (APMs), a key component of the latest proposed reforms under MACRA, build on the delivery and payment reforms that we have experimented with over the past 5 years. These include: 1) Medicare and Medicaid Electronic Health Record Incentive Programs, also known as ?Meaningful Use? (MU), which pay providers for adopting and using certified electronic health records for core clinical documentation; 2) Patient-Centered Medical Home (PCMH) programs that target care processes that ensure that primary care is accessible, well-coordinated, and team-based; and 3) Accountable Care Organization (ACO) programs that align financial incentives of primary care providers, hospitals, and other providers to improve quality and value. Each of these programs has an associated body of evidence that examines its effectiveness. However, research to date has not identified the patterns of primary care provider participation, and how the combination and sequencing interact to affect the magnitude of resulting gains. Our project is focused on capturing participation patterns and near-term effects of MU and PCMH programs in the context of ACO efforts because these are key components of APMs. They are also all voluntary programs, and voluntary participation is expected to be emphasized by the new Administration. We propose to examine a set of outcomes that are expected to improve under these programs: adherence to evidence-based care, reductions in avoidable hospital utilization (e.g., ambulatory-care sensitive admissions), and reductions in spending. We plan to use secondary data sources that capture primary care provider participation in MU, PCMH, and ACO programs along with Medicare claims data on patient outcomes to (1) Identify patterns of primary care practice participation in delivery system reform efforts (MU and PCMH) and payment reform (ACOs), and whether patterns vary by practice characteristics; (2) Test the impact of primary care practice participation in delivery system reform efforts (MU and PCMH) on outcomes targeted by these programs; and (3) Test the extent to which primary care practice participation in payment reform (ACOs) impacts the magnitude of gains from engagement in delivery system reform efforts. Our study is significant because it systematically assesses the impact of the major policy efforts to improve primary care. Our study is innovative because it explores the interactions between the varied delivery and payment reform efforts in order to inform the likely impact of APMs and guide the design of future policies.